﻿Shader "Unlit/Light2D"
{
    Properties
    {
        _MainTex ("Texture", 2D) = "white" {}
    }
    SubShader
    {
        Tags { "RenderType"="Transparent" "Queue" = "Transparent"}
        Blend SrcAlpha OneMinusSrcAlpha
        LOD 100

        Pass
        {
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag

            #include "UnityCG.cginc"

            struct appdata
            {
                float4 vertex : POSITION;
                float2 uv : TEXCOORD0;
            };

            struct v2f
            {
                float2 uv : TEXCOORD0;
                float4 vertex : SV_POSITION;
                float4 objPos : TEXCOORD1;
            };

            sampler2D _MainTex;
            float4 _MainTex_ST;

            fixed4 _Color;
            float4 origin;
            float radius;
            float _FadePower;

            v2f vert (appdata v)
            {
                v2f o;
                o.vertex = UnityObjectToClipPos(v.vertex);
                o.uv = TRANSFORM_TEX(v.uv, _MainTex);
                o.objPos = v.vertex;
                return o;
            }

            fixed4 frag (v2f i) : SV_Target
            {
                fixed4 col = tex2D(_MainTex, i.uv)* _Color;
                float dist = length(i.objPos.xy- origin.xy);
                float ratio = pow(dist / radius, _FadePower);
                float centerratio = pow(dist / radius/0.1, _FadePower*0.3);
                col.a = 1-ratio;
                col = lerp(col, saturate(col*2), saturate(1 - centerratio));
                return col;
            }
            ENDCG
        }
    }
}
